Only fail codecov if push or pull request

[jayqi]

Should reduce the noise we get from Codecov being flaky.

Demo in another repo:

• pull_request
• push (when merging into main branch)
• workflow_dispatch

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.4%. Comparing base (d3522c7) to head (7393aba).

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #510     +/-   ##
========================================
- Coverage    93.7%   93.4%   -0.3%     
========================================
  Files          23      23             
  Lines        1798    1798             
========================================
- Hits         1685    1680      -5     
- Misses        113     118      +5     

see 1 file with indirect coverage changes

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